CN111909004A - Method for separating m-cresol from p-cresol - Google Patents

Abstract

The invention discloses a method for separating m-cresol and p-cresol, and relates to the field of fine separation in the technical field of coal chemical industry. The method for separating m-cresol and p-cresol disclosed by the invention comprises the following steps: m-cresol and p-cresol with purity of more than 98% are obtained by taking m-cresol and p-cresol obtained by vacuum rectification of crude phenol as raw materials, adopting common urea and oxalic acid as complexing agents, performing two-step complexing crystallization, and controlling temperature and reaction time in the complexing and crystallization processes. The beneficial effects are as follows: the method aims at the composition characteristics of m-cresol and p-cresol to obtain the optimized process and parameters for refining and separating phenol products; the whole process flow is simple, the product quality is high, the production cost is low, and the method is an economical and feasible m-cresol and p-cresol fine separation process.

Description

Method for separating m-p-cresol

technical field

The present disclosure relates to the field of fine separation in the technical field of coal chemical industry, in particular to a method for separating m-p-cresol.

Background technique

m-p-cresol is a common extract of coal tar crude phenol vacuum distillation. Because m-cresol and p-cresol have similar boiling points, they cannot be separated by conventional rectification. They generally appear as mixed components, and their added value is relatively high. Low. In order to increase the added value, further separation must be carried out to obtain pure products.

At present, the more conventional methods for separating cresol isomers include crystallization separation method, complex addition method, alkylation separation method and molecular sieve adsorption method. For example, the patent whose application number is CN107721827A discloses a method for purifying m-p-cresol. First, crude m-p-cresol is passed into a light-removing tower, and the crude m-p-cresol is rectified to obtain high-purity m-p-cresol by rectification. 2,6-xylenol is then fed into a weight-removing tower for rectification to obtain high-purity o-ethylphenol and m-p-cresol; the patent application number CN106831355A discloses a high-pressure mixed m-p-cresol A method for fixed bed alkylation, wherein the alkylating agent is liquefied under pressure, and then injected into a reactor together with mixed phenol, the pressure of the fixed bed reactor is kept at 1.7-4.2 MPa, the temperature is at 50-110 DEG C, and the temperature is 50-110 DEG C. The reaction rate is 0.1～5h-1, and the self-polymerization product of isobutylene, the mono-tert-butyl product of m-p-cresol and the di-tert-butyl product of m-p-cresol are obtained; the patent application number CN104098445B discloses a kind of from The method for extracting m-cresol from the m-p-cresol mixture, the m-p-cresol mixture and urea are combined into a solid, the obtained solid is washed with a mixed solvent, the washed solid is hydrolyzed with water, the oil phase is separated, and the oil phase is distilled under reduced pressure. Obtain m-cresol. Patent Application No. CN106810422A A kind of method for separating m-p-cresol by liquid-phase alkylation method, which utilizes isobutene gas mixture and m-p-cresol mixture simultaneously in liquid phase to generate alkylation reaction through fixed bed reactor And the new process of separating and obtaining m-cresol and p-cresol, using isobutene gas mixture as alkylating agent, m-p-cresol mixture as raw material, through liquid-phase alkylation reaction and separation to obtain m-cresol and p-cresol pure products . The patent with the application number of CN104496759A discloses a kind of m-p-cresol separation, which uses m-p-cresol mixed liquid and isobutylene gas as raw materials, and uses immobilized acidic ionic liquid as a catalyst to generate an alkylation reaction in a fixed bed, and will obtain The mono-tert-butyl cresol is de-tert-butylated to obtain high-purity m-cresol and p-cresol.

In the above methods, there are problems such as large equipment investment, high energy consumption, or equipment corrosion.

SUMMARY OF THE INVENTION

The purpose of the present disclosure is to overcome the deficiencies of the prior art, and to provide a method for separating m-p-cresol with low equipment investment, low energy consumption, little corrosion to equipment and simple process flow.

The method for separating m-p-cresol provided by the present disclosure, its technical scheme is:

It includes the following steps:

(1) Separation of m-cresol:

Weigh the mixed phenol of quantitative m-p-cresol and put it into the reactor. Based on m-cresol, first add an appropriate amount of complexing agent urea, stir, heat and heat up to 50-90 ° C, stop heating, and carry out complex reaction. , when the feed liquid is naturally cooled to 35-45 ℃, start to drip toluene into the reactor, the temperature of the feed liquid continues to decrease, when the temperature is cooled to -15-5 ℃, stop the dropwise addition of toluene, and carry out cooling crystallization; then filter , and wash the filter cake with toluene; Dissolve the filter cake with distilled water at last, obtain the upper oil phase after the liquid separation, and distill the oil phase to obtain m-cresol;

(2) Separation of p-cresol:

After separation of m-cresol, the remaining phenol liquid is mainly p-cresol. Based on p-cresol, an appropriate amount of oxalic acid is added first, and after stirring and heating to 80-110 ° C, the complexation reaction is carried out for a certain period of time, and toluene is added dropwise. , the temperature of the feed liquid is continuously reduced, when the temperature of the feed liquid is statically cooled to -5～10 ℃, stop dripping toluene; then suction filtration to obtain a white solid; finally, use 30～40 ℃ of hot water to hydrolyze the white solid to separate liquid After the upper oil phase steams toluene and water under normal pressure, under vacuum conditions, the fractions are cut by vacuum distillation to obtain the p-cresol product;

(3) Solvent reuse:

The toluene steamed in the separation steps (1) and (2) is separated, and the toluene is purified by distillation, and the toluene is cyclically applied.

The present disclosure first separates and extracts m-cresol in m-p-cresol by using urea as a complexing agent, and then uses oxalic acid as a complexing agent to separate and extract m-cresol in the phenol solution after extracting the cresol. Separation and extraction, the separation of m-p-cresol can be realized through the two-step separation. The separation method has low investment in production equipment, low corrosiveness to equipment, and low energy consumption, which is convenient for industrialization promotion; and the entire disclosure of the present disclosure. The technological process is reasonable, the product quality is high, and the production cost is low, and it is an economical and feasible fine separation process of m-p-cresol.

Wherein, in step (1), the ratio of the amount of the complexing agent urea to m-cresol is 0.8-1.4.

Wherein, in step (1), after stirring and heating to raise the temperature to 70-80° C., the heating is stopped to carry out the complexation reaction.

Wherein, in step (1), when the temperature is cooled to -15～-10°C, the dropwise addition of toluene is stopped, and cooling crystallization is performed.

Wherein, in step (1), the volume of toluene added dropwise to the reactor is 2 to 4 times the volume of the mixed phenol of m-p-cresol.

Wherein, in step (2), the material ratio of oxalic acid to p-cresol is 1-1.3.

Wherein, in step (2), after stirring and heating to 95-105° C., the complexation reaction is carried out for a certain period of time.

Wherein, in step (2), when the temperature of the feed liquid is statically cooled to 0-5° C., the dropwise addition of toluene is stopped.

Wherein, in step (2), in the process of separating p-cresol, the volume of toluene added dropwise to the reactor is 2-4 times the volume of the phenol liquid.

Detailed ways

The implementations described in the following exemplary disclosure are not intended to represent all implementations consistent with this disclosure. Rather, they are merely examples of apparatus and methods consistent with some aspects of the present disclosure as recited in the appended claims.

A kind of method for separating m-p-cresol provided by the invention, comprises the steps:

(1) Separation of m-cresol: weigh the mixed phenol of quantitative m-p-cresol and put it into the reactor, take m-cresol as a benchmark, add an appropriate amount of complexing agent urea first, stir, heat and heat up to 50～90 ℃ , stop heating, carry out the complexation reaction, when the feed liquid is naturally cooled to 35-45 ℃, start to drip toluene into the reactor, the temperature of the feed liquid continues to decrease, when the feed liquid temperature is cooled to -15-5 ℃, stop Add toluene dropwise to crystallize by cooling; then filter, and wash the filter cake with toluene; finally dissolve the filter cake with distilled water, obtain the upper oil phase after liquid separation, and distill the oil phase to obtain m-cresol;

(2) Separation of p-cresol: after separation of m-cresol, the remaining phenolic solution is mainly p-cresol. Based on p-cresol, an appropriate amount of oxalic acid is firstly added, stirred and heated to 80-110° C., and then complexed. After the reaction for a certain period of time, the dropwise addition of toluene was started, and the temperature of the feed liquid continued to decrease. When the temperature of the feed liquid was statically cooled to -5～10°C, the dropwise addition of toluene was stopped; then suction filtration was performed to obtain a white solid; The white solid is hydrolyzed with water, and the upper layer oil phase is obtained after the liquid separation. The upper layer oil phase is distilled to obtain toluene and water under normal pressure, and the fractions are cut by vacuum distillation under vacuum conditions to obtain the p-cresol product;

(3) Reuse of solvent: separate the toluene steamed in steps (1) and (2), purify the toluene by distillation, and apply it cyclically.

The present disclosure first separates and extracts m-cresol in m-p-cresol by using urea as a complexing agent, and then uses oxalic acid as a complexing agent to separate and extract m-cresol in the phenol solution after extracting the cresol. Separation and extraction, the separation of m-p-cresol can be realized through the two-step separation. The separation method has low investment in production equipment, low corrosiveness to equipment, and low energy consumption, which is convenient for industrialization promotion; and the entire disclosure of the present disclosure. The technological process is reasonable, the product quality is high, and the production cost is low, and it is an economical and feasible fine separation process of m-p-cresol.

Preferably, in step (1), the ratio of the amount of the complexing agent urea to m-cresol is 0.8-1.4.

Preferably, in step (1), after stirring and heating the temperature to 70-80° C., the heating is stopped to carry out the complexation reaction.

Preferably, in step (1), when the temperature is cooled to -15～-10°C, the dropwise addition of toluene is stopped, and cooling crystallization is performed.

Preferably, in step (1), the volume of toluene added dropwise to the reactor is 2 to 4 times the volume of the mixed phenol of m-p-cresol.

Preferably, in step (2), the material ratio of oxalic acid to p-cresol is 1-1.3.

Preferably, in step (2), the complexation reaction is carried out for a certain period of time after stirring and heating to 95-105°C.

Preferably, in step (2), when the temperature of the feed liquid is statically cooled to 0-5° C., the dropwise addition of toluene is stopped.

Preferably, in step (2), in the process of separating p-cresol, the volume of toluene added dropwise to the reactor is 2-4 times the volume of the phenol liquid.

The method for separating m-p-cresol of the present invention will be described in detail below through specific examples.

Example 1:

(1) Separation and purification of m-cresol: weigh 200g of mixed phenol raw material and put it into the reactor. In the mixed phenol raw material, m-cresol accounts for 60.0% and p-cresol accounts for 40.0%. According to the ratio of the amount of the complexing agent urea to m-cresol, it is 1.2:1, after adding 84 g of the complexing agent urea, stirring and warming up to 80 ° C, stop heating, carry out the complexing reaction, and wait for the temperature of the feed liquid to be naturally cooled to At 40°C, the dropwise addition of toluene was started, and the temperature of the feed liquid continued to decrease. When the dropwise addition amount of toluene was 600 mL, and the temperature of the feed liquid was cooled to -15°C, the dropwise addition of toluene was stopped, and cooling crystallization was performed; then filtered, and washed with toluene. cake, finally dissolve the filter cake with distilled water, obtain the upper oil phase after the liquid separation, distill the upper oil phase to obtain 97.3 g of m-cresol product, and its content reaches 98.7%;

(2) Separation and purification of p-cresol: After separation of m-cresol, the composition content of the remaining phenol liquid is p-cresol accounting for 76.6% and m-cresol accounting for 23.4%. The main ingredient is p-cresol. Based on p-cresol, the oxalic acid complex method is used to separate p-cresol. According to the ratio of oxalic acid and p-cresol to 1.2:1, add 68g oxalic acid, stir and heat to 100 ℃, After the reaction for 2.5 hours, the dropwise addition of toluene was started, and the temperature of the feed liquid continued to decrease. When the dropwise addition amount of toluene was 350 mL, and the temperature of the feed liquid was statically cooled to 5 °C, the dropwise addition of toluene was stopped, and the cooling process took about 15 hours; then suction filtration, A white solid was obtained, which was finally hydrolyzed with hot water at 30 to 40° C. The oil phase after the liquid separation was distilled to extract toluene and water under normal pressure, and then the fractions were cut under reduced pressure under vacuum to obtain 72.5 g of p-cresol product. up to 99.0%.

(3) Reuse of solvent: separate the toluene steamed in steps (1) and (2), purify the toluene by distillation, and apply it cyclically.

Example 2:

(1) Separation and purification of m-cresol: weigh 200g of mixed phenol raw material and put it into the reactor. In the mixed phenol raw material, m-cresol accounts for 50.9%, p-cresol accounts for 34.1%, and 2,6-xylenol accounts for 50.9%. 6.1%, 2-ethyl phenol accounts for 8.9%, based on m-cresol, first add 72g of complexing agent urea according to the ratio of the amount of complexing agent urea to m-cresol is 1.2:1, stir, heat up After reaching 80°C, the heating was stopped, and the complexation reaction was carried out. When the temperature of the feed liquid was naturally cooled to 40°C, toluene was added dropwise, and the temperature of the feed liquid was continuously reduced. At 10°C, the dropwise addition of toluene was stopped, and cooling crystallization was carried out; then suction filtration, washing the filter cake with toluene, and finally dissolving the filter cake with distilled water, after liquid separation, the upper oil phase was obtained, and the upper oil phase was distilled to obtain 81.7 g of m-cresol product, Its content is 99.1%;

(2) Separation and purification of p-cresol: after separation of m-cresol, the composition content of the remaining phenol liquid is p-cresol accounting for 57.7%, m-cresol accounting for 17.0%, 2-ethylphenol accounting for 15.0%, 2,6-bis-cresol accounting for 15.0%, Cresol accounted for 10.3%. The main ingredient is p-cresol. Based on p-cresol, the p-cresol is separated by the oxalic acid complex method. According to the ratio of oxalic acid to p-cresol, 60g of oxalic acid is added, and the mixture is stirred and heated to 100°C. After the reaction for 2 hours, the dropwise addition of toluene was started, and the temperature of the feed liquid continued to decrease. When the dropwise amount of toluene was 300 mL, and the temperature of the feed liquid was statically cooled to 5 °C, the dropwise addition of toluene was stopped, and the cooling process took about 15 hours; then suction filtration to obtain The white solid was finally hydrolyzed with hot water at 30-40°C, the oil phase after the liquid separation was distilled off toluene and water under normal pressure, and then the fractions were cut under reduced pressure under vacuum to obtain 55.4 g of p-cresol product with a content of 99.0%.

(3) Reuse of solvent: separate the toluene steamed in steps (1) and (2), purify the toluene by distillation, and apply it cyclically.

Example 3:

(1) Separation and purification of m-cresol: weigh 300 g of mixed phenol raw material and put it into the reactor. In the mixed phenol raw material, m-cresol accounts for 50.9%, p-cresol accounts for 34.1%, (m-cresol 50.9%, p-cresol 34.1%) Cresol 34.1%, 2,6-xylenol 6.1%, 2-ethylphenol 8.9%, based on m-cresol, the ratio of the amount of complexing agent urea to m-cresol is 1.25: 1 After adding 106g of complexing agent urea, stirring and warming up to 75°C, stop heating and carry out complexation reaction. When the temperature of the feed liquid is naturally cooled to 40°C, toluene is added dropwise, and the temperature of the feed liquid is continuously reduced. The dosage is 800 mL, and when the temperature of the feed liquid is cooled to -15 °C, the dropwise addition of toluene is stopped, and cooling crystallization is carried out; then filter, and wash the filter cake with toluene, and finally dissolve the filter cake with distilled water, obtain the upper oil phase after liquid separation, and distill the upper oil 130.8 g of m-cresol products were obtained, with a content of 99.2%.

(2) Separation and purification of p-cresol, after separation of m-cresol, the composition content of the remaining phenol liquid is p-cresol 60.4%, m-cresol 13.5%, 2-ethylphenol 15.5%, 2,6-xylenol 10.6% %. The main ingredient is p-cresol, and the p-cresol is separated by oxalic acid complexation. Taking p-cresol as the benchmark, 110 g of oxalic acid is added according to the ratio of oxalic acid and p-cresol to 1.3:1, heated to 100 ° C, and the reaction is carried out. After 2.5 hours, the dropwise addition of toluene was started, and the temperature of the feed liquid continued to decrease. When the dropwise amount of toluene was 500 mL, and the temperature of the feed liquid was statically cooled to 5 °C, the dropwise addition of toluene was stopped, and the cooling process took about 15 hours; then suction filtration to obtain The white solid was finally hydrolyzed with hot water at 30-40°C, the oil phase after the liquid separation was distilled off toluene and water under normal pressure, and then the fractions were cut under reduced pressure under vacuum to obtain 83.1 g of p-cresol product with a content of 99.1%.

(3) Reuse of solvent: separate the toluene steamed in steps (1) and (2), purify the toluene by distillation, and apply it cyclically.

Other embodiments of the present disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or techniques in the technical field not disclosed by the present disclosure . The specification and disclosure are to be regarded as exemplary only, with the true scope and spirit of the disclosure being indicated by the following claims.

It should be understood that the present disclosure is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims (9)

1. the method for separating m-p-cresol, is characterized in that, comprises the steps: (1) Separation of m-cresol: Weigh the mixed phenol of quantitative m-p-cresol and put it into the reactor. Based on m-cresol, first add an appropriate amount of complexing agent urea, stir, heat and heat up to 50-90 ° C, stop heating, and carry out complex reaction. , when the feed liquid is naturally cooled to 35-45°C, start to drip toluene into the reactor, and the temperature of the feed-liquid decreases continuously; when the feed-liquid temperature is cooled to -15-5°C, stop the dropwise addition of toluene, and carry out cooling crystallization; Then filter, and wash the filter cake with toluene; Dissolve the filter cake with distilled water at last, obtain the upper oil phase after the liquid separation, and distill the oil phase to obtain m-cresol; (2) Separation of p-cresol: After separation of m-cresol, the remaining phenolic liquid is mainly p-cresol. Based on p-cresol, first add an appropriate amount of oxalic acid, stir and heat up to 80-110 ° C, and after a certain time of complexation reaction, start to add toluene dropwise , the temperature of the feed liquid is continuously reduced, when the temperature of the feed liquid is statically cooled to -5～10 ℃, stop dripping toluene; then suction filtration to obtain a white solid; finally, use 30～40 ℃ of hot water to hydrolyze the white solid to separate liquid After obtaining the upper oil phase, the upper oil phase distills toluene and water under normal pressure, and cuts the fractions under vacuum rectification to obtain the p-cresol product; (3) Solvent reuse: The toluene steamed in the separation steps (1) and (2) is separated, and the toluene is purified by distillation, and the toluene is cyclically applied. 2 . The method for separating m-p-cresol according to claim 1 , wherein, in step (1), the ratio of the amount of the complexing agent urea to m-cresol is 0.8 to 1.4. 3 . 3. The method for separating m-p-cresol according to claim 1 or 2, characterized in that, in step (1), after stirring and heating to 70-80° C., the heating is stopped and the complexation reaction is carried out. 4. the method for separating m-p-cresol according to claim 1 and 2, is characterized in that, in step (1), when temperature is cooled to -15～-10 ℃, stop dripping toluene, and carry out cooling crystallization . 5. the method for separating m-p-cresol according to claim 1 and 2, is characterized in that, in step (1), the volume of the toluene that drips in reactor is the mixed phenol volume of m-p-cresol 2 to 4 times. 6 . The method for separating m-p-cresol according to claim 1 , wherein, in step (2), the material ratio of oxalic acid to p-cresol is 1 to 1.3. 7 . 7. The method for separating m-p-cresol according to claim 1 or 6, characterized in that, in step (2), after stirring and heating to 95-105° C., the complexation reaction is carried out for a certain period of time. 8. The method for separating m-p-cresol according to claim 1 or 6, characterized in that, in step (2), when the temperature of the feed liquid is statically cooled to 0～5°C, the dropwise addition of toluene is stopped. 9. the method for separating m-p-cresol according to claim 1 or 6, is characterized in that, in step (2), in separating p-cresol process, the volume of the toluene dripped in reactor is phenol 2-4 times the volume of the liquid.